Technical Field
The present disclosure relates generally to an anvil assembly having a tiltable head which is suitable for use with a circular anastomosis stapler. More specifically, the present disclosure relates a tiltable anvil assembly having a frangible retaining member.
Background of Related Art
Circular anastomosis staplers which include an anvil assembly having a tiltable anvil head are known in the art. An example of such circular anastomosis stapler and tiltable anvil assembly are disclosed in commonly owned U.S. Pat. No. 7,364,060 (“the '060 patent”). A further example of a tiltable anvil assembly is disclosed in commonly owned U.S. Patent Application Publication No. 2008/0230581 (“the '581 publication”). The content of each of the '060 patent and the '581 publication are hereby incorporated herein by reference in their entirety. The anvil assembly described in the '581 publication includes a backup plate located within the anvil assembly positioned to prevent tilting of the anvil head of the anvil assembly prior to firing of the stapler. Upon firing of the stapler, a knife blade of the stapler engages and moves the backup plate to a position which allows the anvil head to tilt upon retraction of the knife blade. If the backup plate sticks to the knife blade upon retraction of the knife blade, the backup plate may return to its position preventing tilting of the anvil head. When this occurs, the anvil head will not tilt.
In order to maintain the backup plate in a proximal position where it prevents tilting of the anvil head prior to firing, the anvil assembly described in the '581 publication includes a retainer member positioned distal of the backup plate. The retainer member includes a plurality of deformable tabs which prevent distal movement of the backup plate until a predetermined force sufficient to deform the tabs is applied to the backup plate, i.e., through engagement with the knife blade during staple formation. A residual proximal force is produced during deformation of the deformable tabs. This force acts on the backup plate which may cause the backup plate to move proximally towards its original position. As described in the '581 publication, the tilting operation of the anvil assembly relies on the distal positioning of the backup plate following the firing of the stapler. Any proximal force that acts on the backup plate may cause the backup plate to return to the original proximal position, thereby preventing tilting of the anvil assembly.
Therefore, it would be beneficial to provide an anvil assembly with a means of retaining the backup plate in the proximal position prior to firing of the stapling assembly, that allows the backup plate to move to the distal position during firing of the stapling assembly, and that does not produce a proximal force which acts on the backup plate after firing of the stapling assembly that may prevent the anvil assembly from tilting.